How does geothermal heating work? A homeowner's view
Home geothermal heating takes low-grade heat from the ground through a buried loop and lifts it with a heat pump to a useful temperature for the house. The ground a few metres down stays near the yearly average air temperature, so the loop has a steadier heat source than outdoor air.
What does geothermal heating mean for a house?
The word covers two very different things. Large geothermal plants tap hot rock or water deep underground to make electricity or supply heat to whole towns. A home system is much simpler. It uses the shallow ground, usually within about a hundred metres of the surface, as a place to take heat from in winter and dump heat into in summer. That is why it is also called a ground-source or geoexchange system.
Most of the warmth in the shallow ground comes from the sun and the seasons, not from deep inside the Earth. The steadiness of that temperature is explained in ground temperature by depth in Canada.
How does the system move heat into the house?
Three circuits are linked. In the buried loop, a mix of water and antifreeze circulates, picking up heat from the ground. Inside the heat pump, a refrigerant cycle takes that heat, compresses it to a higher temperature and passes it to the house's own distribution system, either warm air through ducts or warm water for floor heating or radiators. In summer the cycle reverses, so geothermal systems also provide cooling, and many can supply hot water as well. That makes geothermal heating a year round system for energy use in the home.
The heat pump does not make heat from nothing. It uses electricity to move several units of heat for each unit of electricity consumed. The cycle in detail is in the guide to how ground-source heat pumps work.
What does the buried loop look like?
Loops are either vertical boreholes, drilled to a depth set by the design, or horizontal trenches, which need more land. Some sites use a pond or an open-loop well instead. The choice depends on the lot, the soil and rock and the local rules, and the guide to horizontal and vertical ground loops compares them. Because the underground loop is buried, it is out of sight and out of the weather, and its pipes are expected to outlast the equipment indoors.
How is this different from solar heat stored in the ground?
At Drake Landing, the ground was a battery, not a source. Solar collectors heated water in summer, and that heat was pushed into 144 boreholes under a park, then drawn back out through the winter to warm 52 homes through a district loop. The heat came from the sun, and the ground simply held it for months. The design is described in borehole storage at Drake Landing and in the explainer on borehole thermal energy storage.
A home geothermal system takes the heat that is already there and relies on a heat pump to lift it. The two ideas share the borehole technology and the steady ground, which is why they are often discussed together.
Is geothermal heating a fit for your house?
It suits houses with enough land or room to drill, and owners who value low running costs and plan to stay long enough to repay a high installation price. Heating a well-insulated home with low-temperature floor heating gives the most efficient geothermal heat pumps and systems, as explained in low-temperature hydronic heating. For the money side, see geothermal heat pump cost in Canada and are geothermal heat pumps worth it, which lay out the trade-offs without a single price.
Quick answers
Is geothermal heating the same as a ground-source heat pump?
For a home, yes in practice. Geothermal heating usually means a ground-source heat pump with a buried loop. Large geothermal plants that use deep hot water are a different thing.
Where does the heat in the ground come from?
The shallow ground stores mostly solar heat from the seasons. Only at much greater depth does heat from inside the Earth become the main source.
Does geothermal heating work in cold winters?
Yes. The ground stays well above the winter air temperature, so output does not fall off the way an air-source unit's does, though the loop must be sized for the coldest weather.
Is Drake Landing a geothermal system?
No. It stored heat from solar collectors in the ground and used a district loop. It shares the borehole technology but not the heat source.